Swa main incomer size

[shanky887614]

Not always, a Double pole or a TPSN/four pole isolator isolates the neutral.
And most plug and socket arrangements used for isolation will isolate the earth.

our 4pole isolators early make, late break

have a seperate earth and n connection as well mate.

buy a different brand then mate

 

[davesparks]

our 4pole isolators early make, late break

have a seperate earth and n connection as well mate.

buy a different brand then mate

Why would you need a seperate N in a four pole isolator? That's what the fourth pole is there for!

And I am quite happy with the brand if isolator I use, MEM are tried and tested.

 

[shanky887614]

Why would you need a seperate N in a four pole isolator? That's what the fourth pole is there for!

And I am quite happy with the brand if isolator I use, MEM are tried and tested.

really? we have controls going through our isolators as well sometimes depending on spec

 

[davesparks]

Having controls through a pole of an isolator sounds quite unusual.
Id expect to see control circuits use auxiliary contacts, but then I guess it depends on the equipment and budget.

 

[Knobhead]

For Christ’s sake!

You use 3P+N or SP+N never 4P for distribution!

 

[Knobhead]

It would be great if people learnt the difference between 3P+N and 4P. As Shanky rightly said in a 3P+N the neutral is early make late break. The reason, because you will get voltage imbalance akin to a floating neutral.




I’ve only ever specified four pole ACB/MCCB’s twice in 40 years.

Both breakers were for a 2.6MW 660V two wire earth free system. Four pole because I put two poles in series to handle the fault current. If you look at the manufacturer’s maximum fault current tables for 400V against 690V it drops dramatically!

 

[Engineer54]

It would be great if people learnt the difference between 3P+N and 4P. As Shanky rightly said in a 3P+N the neutral is early make late break. The reason, because you will get voltage imbalance akin to a floating neutral.
I’ve only ever specified four pole ACB/MCCB’s twice in 40 years.

Both breakers were for a 2.6MW 660V two wire earth free system. Four pole because I put two poles in series to handle the fault current. If you look at the manufacturer’s maximum fault current tables for 400V against 690V it drops dramatically!

Yep, all our 2.5-3.2 KA main switchboard TX ACB incomers and the bus couplings are 3 Pole + N with the early make late break function.

 

[davesparks]

For Christ’s sake!

You use 3P+N or SP+N never 4P for distribution!

Sorry Tony, I'm mixing manufacturers terminology with the correct terminology.